I know there is no commercial value in it, so it won'thappen, but wouldn't it be nice if IBM realeased asoftware emulation that worked like the originalXT/370 that emulated both the Hardware and CP callsand so would allow CMS itself to be run native onLinux or Windows..... oh and of course would license CMS for suchan evironment.

XT/370 was codenamed washington ... stripped down CP kernel running onmodified 68k processor that provided 370 emulation (for problem and someprivileged instructions). The "370" had its own dedicate processormemory. Running under dos was a program called "cp/88" and the CP kernelwould communicate with "cp/88" for emulation of I/O operations(i.e. cp/88 provided real device i/o support and communicated back andforth with the cp kernel).

the original model had 384k "370" memory ... and I did some applicationstudies which showed that after the fixed cp kernel memory requirements... that cms applications frequently would "page thrash" in theremaining real memory. Exaserbating the problem was that all disk i/o(both cp paging and cms file i/o) involved communication with cp/88which would then simulate the operations on XT hard disk that had110millisecond avg. access.

the publishing of the elapsed time & page thrashing results resulted ina corporate decision to ship the product with 512k "370" memory... which involved a six month schedule slip ... which lots of peopleblaimed on me.

However, in this time window ... I was allowed to incorporate anenhanced page replacement algorithm (over and above what i was able toship in the vm370 resource manager) ... and CMS "paging access method"filesystem support ... i.e. page-mapped operation ... which I hadoriginally done on cp67/cms ... but never shipped in standard vm370release.

the problem was that normal CMS operations are highly disk intensive.DCSS sharing of applications on mainframes were somewhat able tocompensate for some of this (by having programs & applications alreadyavailable in real storage because of use by other users). However, inthe xt/370 configuration none of this was applicable ... there wasn'tenuf real storage for such caching ... and since it was a single usersystem ... there wasn't any "sharing" use. however, I had demonstratedavg of 300percent (or better) thruput improvement with the paged mappedcms filesystem support for disk intensive operations. The page mappedCMS filesystem support also allowed for asyncronous operation on programloading ... allowing large block load of CMS "module" into whateveravailable real storage ... but also allowing some asyncronous overlap ofCMS application execution with loading of the program (keeping all theasyncronous activity straight and hidden from cms by playing games withpage invalid/valid bits). The page mapped CMS filesystem support alsohad some enhancements for attempting to do contiguous (physical)allocation when MODULE was generated (and/or written to disk) ... whichcould be subsequently leveraged when program was loaded.

the same adapter board was later made available in ATs and calledAT/370.

the "follow-on" was a full-blown 370 in separate box with 4mbytesof memory code-name "a74" (for the department in POK) and releasedas 7437 ... old email with announcement of 7437http://www.garlic.com/~lynn/2000e.html#email880622

old email that includes list of source update files that I had to the cpkernel as part of A74 support ("dmkpam" is the source routine containingthe cp changes supporting paged mapped operation).http://www.garlic.com/~lynn/2003f.html#56 ECPS:VM DISPx instructions

other past posts mentioning A74:http://www.garlic.com/~lynn/2000e.html#55 Why not an IBM zSeries workstation?http://www.garlic.com/~lynn/2000e.html#56 Why not an IBM zSeries workstation?http://www.garlic.com/~lynn/2001i.html#19 Very CISC Instuctions (Was: why the machine word size ...)http://www.garlic.com/~lynn/2001i.html#51 DARPA was: Short Watson Biographyhttp://www.garlic.com/~lynn/2002d.html#4 IBM Mainframe at homehttp://www.garlic.com/~lynn/2002l.html#27 End of Moore's law and how it can influence job markethttp://www.garlic.com/~lynn/2003h.html#40 IBM system 370http://www.garlic.com/~lynn/2003m.html#15 IEFBR14 Problemshttp://www.garlic.com/~lynn/2004l.html#65 computer industry scenairo before the invention of the PC?http://www.garlic.com/~lynn/2004m.html#7 Whatever happened to IBM's VM PC software?http://www.garlic.com/~lynn/2004m.html#8 Whatever happened to IBM's VM PC software?http://www.garlic.com/~lynn/2004m.html#10 Whatever happened to IBM's VM PC software?http://www.garlic.com/~lynn/2007c.html#14 How many 36-bit Unix ports in the old days?http://www.garlic.com/~lynn/2007g.html#76 The Perfect Computer - 36 bits?

old email mentioning some of the activity porting enhancements fromcp67 to vm370http://www.garlic.com/~lynn/2006v.html#email731212http://www.garlic.com/~lynn/2006w.html#email750102http://www.garlic.com/~lynn/2006w.html#email750430

Well, it's been nigh on 40 years that CMS has been around. Seems like acommittment to me. CMS is here to stay. If all the people with z/OSget z/VM and [re]discover CMS, who knows what might happen? "Never saydie!"

re:http://www.garlic.com/~lynn/2007j.html#41 z/VM usability

well, cms (as in cambridge monitor system) started on cp40 (cambridge hadgotten a 360/40 and did the hardware modifications to implement virtualmemory ... pending getting 360/67) ... cambridge got 360/67 in 1967 andmorphed cp40 into cp67 ... so it has been 40yrs (in part, CMS workcould even start on real 360/40 before cp40 was operational)

from Melinda's historyhttp://www.princeton.edu/~melinda/

By September of 1965, file system commands and macros already lookedmuch like those we are familiar with today: ``RDBUF'', ``WRBUF'',``FINIS'', ``STATE'', etc

... snip ...

cambridge installed cp67 out at lincoln labs in 1967 and then last weekin jan68 came out to install cp67 at the univ where i was undergraduate.Note, that in jan68, the cp67 people were still apprehensive about CMSfilesystem ... with cp67 source, assemble, and build still being done onos/360.

in the morph of cp67 to vm370 ... they changed the cms name toconversational monitor system.

major change in cms from cp67 to vm370 was a little re-arranging of cmskernel in anticipation of 370 (r/o) segment protection. However, indoing the virtual memory hardware retrofit to 370/165 ... they ran intoproblem with schedule slipping. In order to regain six months in theschedule for 370/165 virtual memory, they dropped r/o segment protectand some number of other features from the original 370 virtual memoryarchitecture (and to have compatibility across the 370 product line... the same features had to also be removed from other 370 models thatalready had implemented the full 370 virtual memory architecture). With370 hardware r/o segment protect dropped ... vm370 had to revert to thepage protect hack used by cp67 that involved fiddling the 360 storageprotect keys.

Then during the "future system" period ... much of the corporation wasdistracted and a lot of 370 product activity fell by the way side.Misc. past posts about future system:http://www.garlic.com/~lynn/subtopic.html#futuresys

I had made some unflattering comments about practicallity of futuresystem stuff and continued to do both cp67 and cms enhancements ... andthen ported them from cp67 to vm370 ... some old emailhttp://www.garlic.com/~lynn/2006v.html#email731212http://www.garlic.com/~lynn/2006w.html#email750102http://www.garlic.com/~lynn/2006w.html#email750430

after FS was canceled, there was rush to get stuff back into 370 productpipeline. Part of this was reason that small subset of the "virtualmemory management" enhancements ... a lot of shared segment stuffhttp://www.garlic.com/~lynn/subtopic.html#adconthat had been integrated with the paged mapped filesystem stuffhttp://www.garlic.com/~lynn/subtopic.html#mmap

was released as DCSS in vm370 release 3.

Canceling FS contributed to enabling me to also release the resourcemanager (that included a lot of changes that were in cp67 that i haddone ... which were dropped in the morph from cp67 to vm370)http://www.garlic.com/~lynn/subtopic.html#fairsharehttp://www.garlic.com/~lynn/subtopic.html#wsclock

It was also in the aftermath of killing FS that POK convinced thecorporation to kill the vm370 product, shutdown the vm370 product groupand move all the people to POK to help accelerate the mvs/xa developmentschedule (again attempting to make up lost time in 370 product pipelineresulting from the FS distraction). Eventually Endicott was able tosalvage the vm370 product mission.

Well, it's been nigh on 40 years that CMS has been around. Seems like acommittment to me. CMS is here to stay. If all the people with z/OSget z/VM and [re]discover CMS, who knows what might happen? "Never saydie!"

http://www.garlic.com/~lynn/2007j.html#41 z/VM usabilitywell, cms (as in cambridge monitor system) started on cp40 (cambridge hadgotten a 360/40 and did the hardware modifications to implement virtualmemory ... pending getting 360/67) ... cambridge got 360/67 in 1967 andmorphed cp40 into cp67 ... so it has been 40yrs (in part, CMS workcould even start on real 360/40 before cp40 was operational)from Melinda's historyhttp://www.princeton.edu/~melinda/By September of 1965, file system commands and macros already lookedmuch like those we are familiar with today: ``RDBUF'', ``WRBUF'',``FINIS'', ``STATE'', etcIt was also in the aftermath of killing FS that POK convinced thecorporation to kill the vm370 product, shutdown the vm370 product groupand move all the people to POK to help accelerate the mvs/xa developmentschedule (again attempting to make up lost time in 370 product pipelineresulting from the FS distraction). Eventually Endicott was able tosalvage the vm370 product mission.

That POK move convinced the IBM customers (most had VM and many also hadMVS) in this town that IBM was not considering its customers' bestinterests, and it was time to start moving to enterprise SUN boxes,which led to marginal future for major OS staff and IBM support staff,which sped up the transition, resulting in remaining legacy apps beingrun on one machine in an IBM owned bureau, supported by IBM, and mostIBM staff in the city getting packages or finding jobs elsewhere.So it is with the cariboo!